1. Imaging Findings

Based on the provided MRI sequences of the lumbar spine, the following observations are noted:

• The morphology of the lumbar vertebral bodies is generally well-maintained, with no obvious signs of acute fractures or significant structural destruction.
• No significant acute collapse of the intervertebral discs is observed, although some discs show degenerative changes.
• There is no clear intraspinal lesion or evident nerve root compression.
• The paraspinal muscle groups (especially the erector spinae) display heterogeneous signal changes, with varying degrees of fatty infiltration and atrophy, suggesting muscle degeneration or specific pathological processes.

These imaging findings correlate with the clinical presentation of difficulty in extending the lower back, indicating potential chronic weakness or disease in the paraspinal muscles.

2. Potential Diagnoses

Considering the patient’s clinical symptoms (lower back discomfort after prolonged standing and walking, progressive difficulty maintaining upright posture and gait disturbance, without marked upper or lower limb neurological deficits) alongside the imaging findings (fatty infiltration and atrophy of the paraspinal muscles), the following differential diagnoses are proposed:

1. Camptocormia (Bent Spine Syndrome): Commonly seen in Parkinson’s disease, dystonic disorders, and certain muscular diseases. Patients typically report excessive forward flexion of the trunk while standing or walking, with symptom relief in the supine or seated position. Imaging often shows atrophy of the paraspinal muscles.
2. Specific Neuromuscular Disorders (e.g., inclusion body myositis): Characterized by chronic proximal or axial muscle weakness and structural changes, where MRI may reveal heterogenous changes and fatty infiltration in the paraspinal musculature.
3. Drug-Induced Postural Abnormalities: Rare, but certain antipsychotics or anticonvulsants can lead to dystonia and should be considered if relevant medical history is present.
4. Other Uncommon Causes (e.g., paraneoplastic syndromes, Grave’s disease): These are less frequent and require correlation with systemic symptoms and respective evaluations.

The differential diagnosis is primarily based on the patient’s presenting bent spine posture, paraspinal muscular weakness, and imaging evidence of muscle atrophy.

3. Final Diagnosis

Taking into account the patient’s age, clinical symptoms (progressive difficulty maintaining an upright posture, lower back discomfort), radiological evidence of paraspinal muscle atrophy, and the exclusion of significant nerve root pathology or spinal cord compression, the most likely diagnosis is:

Camptocormia (Bent Spine Syndrome), possibly related to paraspinal muscle atrophy or thoracolumbar muscular insufficiency.

To further characterize any underlying myopathic or neurogenic process, electromyography or muscle biopsy may be considered if inflammatory or neurogenic pathologies are suspected.

4. Treatment and Rehabilitation Plan

Regarding Camptocormia, most patients show limited response to standard medications (e.g., anticholinergics, amantadine, dopamine agonists, muscle relaxants, or tetrahydrobenzazepine), but potential reversible factors (e.g., medication side effects, endocrine abnormalities) should be investigated. Treatment objectives focus on slowing progression and improving the patient’s daily functioning and postural control.

1) Conservative Management

• Medication Adjustment: If the patient also has Parkinson’s disease or dystonic disorders, optimizing the current regimen under specialist guidance may help.
• Braces and Orthotics: For severe postural collapse, a rigid brace or custom-made orthotic device could assist in maintaining a relatively extended spine.

2) Physical Therapy and Rehabilitation

• General Principles: Gradual strengthening exercises targeting core muscles (abdominal muscles and back extensors), paired with stretching and postural training.
• Frequency: Recommended 3–5 sessions per week, based on patient tolerance.
• Intensity: Start with low to moderate intensity, avoiding overexertion or secondary injury. The Borg scale (an RPE of 11–13) can be used for self-assessment.
• Time: Each session should last about 20–30 minutes, potentially divided into segments to prevent excessive fatigue.
• Type: Core stability exercises, back extensor strengthening (e.g., prone back extension, quadruped exercises), and stretches to improve hip joint flexibility.
• Volume & Progression: Increase session duration, range of motion, and resistance (e.g., resistance bands, light dumbbells) according to patient tolerance and muscle strength improvements. Monitor posture and pain responses closely.
• Adjunctive Therapies: Heat therapy, mild physiotherapy, or electrical stimulation may help relax tight muscles or alleviate soreness.

3) Other Possible Treatment Measures

• For cases with marked dystonia or comorbid Parkinson’s disease, deep brain stimulation (bilateral pallidal stimulation) has been reported to provide some functional benefit in a few studies, though clinical application requires strict indications.
• Regular follow-up is recommended to monitor disease progression. EMG, muscle biopsy, and metabolic evaluations should be considered if a treatable or reversible myopathy is suspected.

Safety Considerations

• Older patients may have osteoporosis or reduced cardiopulmonary function. Careful attention should be given to posture transitions during exercise to avoid falls and excessive stress on the lumbar spine.
• If notable worsening of low back pain, numbness, or weakness in the lower limbs occurs during training, re-evaluation is advised to adjust the treatment plan.

Disclaimer: This report is based solely on the provided imaging and clinical data for reference purposes and does not replace in-person consultation or advice from a professional physician. Specific treatment should be determined according to the patient’s actual clinical condition and upon consultation with relevant specialists.